1. Field of the Invention
The present invention relates to a windscreen washer pump, and particularly to a single outlet-type washer pump for use with a vehicle, which serves to supply washer fluid to the windscreen.
2. Description of the Related Art
One type of washer fluid washer pump heretofore used for vehicles is a Westco rotary pump. With this type of pump, washer fluid can be supplied to, for example, a front glass, rear glass or the like at full pressure because washer fluid within a pump chamber can be fully pressurized for spraying it from an outlet.
FIGS. 7 and 8 show a conventional Westco rotary washer pump.
This pump has a pump chamber 24 with a flow channel 30 defined along the outer periphery thereof, and an rotatable impeller 22 within the pump chamber 24. When the impeller 22 is rotated and driven in a direction indicated by the arrow of FIG. 7, the washer fluid supplied from an inlet 14 is fully pressurized within the flow channel 30 and expelled from an outlet 16.
As shown in FIG. 8, the outlet 16 of the washer pump is guided to various spray nozzles 52, 54 provided at the front of the vehicle via piping--including, for example, hoses 50, a three-way joint 60, etc. The illustrated nozzles 52, 54 spray the front windscreen with washer fluid. To reduce the time required from the driving of the pump to the fluid spraying from each nozzle, check valves 56, 58 are provided at intermediate points of the piping arrangement.
In such a washer system, when the washer switch is operated by the user, the pump is driven and the washer fluid within a tank is sprayed through the front nozzles 52, 54 by means of the pump. On the other hand, when the washer fluid within the tank is depleted and the pump runs in an empty state, the hoses 50 in the piping arrangement fills with air.
At this point the user must refill the washer tank before using the washer system.
The conventional washer system is however accompanied by the problem that the fluid does not enter the pump chamber 24 because of the residual air in the hoses 50 and therefore fails to self-prime and become functional again, even when the impeller 22 provided within the pump is rotated and driven.
In particular, in the above-described washer system, it is hard to remove or expel air which exists within the piping arrangement, especially air within the hoses 50 and the pump chamber 24 because of check valves 56, 58 within the piping arrangement. Accordingly, ordinary users cannot easily solve the problem.